A flow carrier may be any structure through which media may be transported. The flow carrier may have a cross-section area that is shaped in a variety of configurations such as circular, square, rectangular, splined, or uneven. The flow carrier may be a tubular. A tubular may be any tube through which material is transported. A tubular may be comprised of a single tube or a series of tubes connected together. A pipeline which transports oil or gas is an example of a tubular. Other examples of tubulars include a well casing within which a work string may be positioned or a well pipe through which hydrocarbons may be produced.
The detection and control of physical conditions (e.g., fluid pressure, fluid speed, etc.) in a tubular are important to ensure the regulated transport and release of materials through and from the tubular. When physical conditions exceed those normally present in the tubular, the materials may be released from the tubular in an uncontrolled manner as for example when a blowout occurs or at an undesired location as for example when the tubular ruptures.
A blowout of an oil or gas well occurs when there is an uncontrolled release of hydrocarbons from the well annulus or bore. The weight of the column of drilling fluid in the well annulus normally exerts sufficient downward force as to control the downhole pressures which force the hydrocarbons upward to the well's surface. When the counter-pressure exerted by the weight of the drilling fluid no longer controls the downhole pressure, a blowout occurs resulting in the uncontrolled release at the well surface of the hydrocarbons.
Blowouts of oil and gas wells are undesired. Blowouts may cause damage to rig equipment and personnel. Blowouts may cause environmental damage or pollution arising from well fires or the deposit of hydrocarbons on land or in the ocean if the blowout occurs on an off-shore rig. The blowout may also result in the loss of economic value as the well reservoir is depleted. There is also the added expense of capping the well and replacing equipment in order to resume normal drilling or production activities.
Blowout preventers have been developed to prevent well blowouts. Most blowout preventers are surface equipment which are manually activated by a member of the drilling or production crew when readings on the master control panel indicate that pressures in the well annulus have increased to a point that a blowout may take place. The crew member presses a switch on the master control panel which causes activation of the blowout preventer. The blowout preventer closes the annulus with two large hydraulic rams or alternatively piston and wedge elements are engaged which squeeze a rubber gasket around the drill pipe to seal the opening between the outer surface of the drill pipe and the well annulus.
Because the crew member may not be paying attention to the pressure readings on the control panel or not appreciate that blowout conditions exist, automatic blowout preventers have been developed.
U.S. Pat. No. 5,507,465 describes an automatic surface blowout preventer. The blowout preventer is activated when the annulus pressure exceeds a preset hydraulic pressure in the fluid chamber of a piston in the blowout preventer. This causes the piston to move upward thereby forcing a wedge assembly to press against the drill pipe extending through the central drill pipe bore of the blowout preventer and into a sealing engagement therewith.
U.S. Pat. No. 3,717,203 describes an automatic subsurface blowout preventer. The blowout preventer is positioned in a flow tube which is connected to a packer. The packer is set in a well pipe or casing. The blowout preventer includes a rigid housing attached to the end of the flow tube. The housing's interior contains a collapsible sleeve made of rubber or a rubber like material. Slots in the housing expose the sleeve to fluid pressure. During normal fluid flow, the sleeve is pressed against the housing's inner wall by the pressure of the fluid flowing upward through the housing. This maintains a flow bore through the sleeve so that the fluid is able to flow from the casing through the bore in the sleeve and up through the tubing to the well surface. When well pressure increases to a point that a blowout may occur, the rapidly flowing fluid creates a pressure drop through the inside of the sleeve so that a pressure differential is created across the wall of the sleeve which is sufficient to collapse the sleeve. This closes the flow bore through the sleeve and stops the upward flow of the fluid to the well surface.
Despite the developments of automatic blowout preventers, the need still exists for an improved blowout preventer that is capable of being integrated with the tubular and which quickly and effectively seals the flow bore in the tubular when conditions require such sealing.
Accordingly, it is an object of the present invention to provide an improved blowout preventer which is capable of being integrated with the tubular and which provides a reliable and effective inflatable sealing mechanism that may be automatically activated upon the detection of possible blowout conditions.
It is to be understood that the present invention is not limited to use as a blowout preventer. The present invention may be used with a variety of flow carriers or tubulars in other applications to seal off the inside of the flow carrier or to seal the flow bore of the tubular.